1. Field of the Invention
The present invention relates generally to the mounting of electronic components on a printed circuit board. More particularly, the present invention relates to apparatus and methods for ensuring alignment (parallelism) of electrical connectors to a printed circuit board during an assembly process.
2. Description of Related Art
Most electronic systems include a printed circuit board with several electronic connectors connected to the circuit board. There are currently numerous electrical connectors available that can be mounted to a printed circuit board. For example, printed circuit boards are connected to cables or other mechanical or electrical mechanical parts of the electronic systems through straddle-mounted (or edge mounted) connectors. The straddle-mounted connectors are attached to an edge of a circuit board such that the connectors straddle or overlap opposing surfaces of the printed circuit board.
U.S. Pat. No. 5,199,855 discloses an example of a connector (trade name: MICTOR, manufactured by AMP Incorporated) that is typically mounted to the edge of the printed circuit board in a straddle-mount configuration. As shown in FIGS. 1-2, a Mictor connector 1 comprises two rows of leads 10 defining a space therebetween for receiving a circuit board 20. The leads 10 engage with conductive pads 30 formed on the circuit board 20 to establish electrical connection between the connector and the circuit board 20. A plurality of through holes are defined in the circuit board 20 proximated and spaced along an edge 25 of the circuit board 20 received in the space between the leads 10. Each through hole 40 has an inner plating electrically connected to a grounding path of the circuit board 20. The connector has a plurality of grounding pins 50 arranged in the space between the leads 10 for extending through the edge 25 of the circuit board 20 to intersect the corresponding through holes 40 to electrically engage the plating, thereby grounding the pins 50 to the circuit board 20. Typically, the leads 10 of the circuit board 20 are connected to the circuit board 20 through the use of solder 60. In addition, two standard size Mictor connectors are typically attached to a standard size circuit board.
Typically, straddle-mounted connectors are solder-connected to a circuit board using a reflow process. The reflow process allows for high volume component soldering in an efficient manner because the parts being soldered can be continuously run through a reflow oven. In practice, however, the conventional reflow assembly process for connecting the connectors to the circuit board is difficult to reproduce in a controllable manner and results in many electrical failures at the connectors of the circuit boards. As shown by connector example in FIGS. 1 and 2, these failures usually occur at the contact points of the straddle-mounted connectors and its corresponding circuit board (e.g., where the leads 10 engage the conductive pads 30) due to misalignment in either the X-direction 90, Y-direction 80 or Z-direction 70. The misalignment may occur during the insertion assembly process (e.g., not placing the connectors in the proper location on the circuit board) and/or the reflow assembly process (e.g., before the solder is re-solidified in the oven, the connectors on the circuit board can easily be displaced by external forces). Thus, in the conventional assembly process, the contact points between the circuit board and the connectors have to be inspected twicexe2x80x94once after the insertion process and again after the reflow process to ensure that the contact points have been properly aligned. Extra labors and associated costs due to these inspections are not minimal. Further, relying on inspection and measurement data to meet the alignment requirements is not a proactive approach to finding the root cause of the problem.
Accordingly, there is a need to provide for apparatus and methods that proactively ensure alignment (parallelism) of the connectors on the circuit board during the assembly process and thereby reduce assembly costs (e.g., reduce the number of reactive inspections and yield loss).
The present invention relates to apparatus and methods that proactively ensure alignment (parallelism) of connectors on a circuit board. The apparatus and methods include an alignment fixture that is adapted to ensure parallelism of the connectors on the circuit board during the solder reflow assembly process. In addition, this fixture helps to determine whether the connectors have been properly aligned on the circuit board after the connectors have been inserted (placed) onto the circuit board (after the insertion assembly process). The fixture also contains a claw to constrain connector displacements during the reflow assembly process. Thus, the present invention provides the important advantage of reducing circuit board assembly costs by proactively ensuring the alignment of the connectors on the circuit board during the assembly process.
In an embodiment of the invention, an apparatus for aligning and soldering connectors onto an edge of a printed circuit board includes a base having a top surface. The top surface has a slot. A first finger clamp is attached to the top surface of the base. The first finger clamp is located between a side of the base and a side of the slot. A claw is coupled to the top surface via the first finger clamp. The claw has a top claw side and a bottom claw side. The bottom claw side is adapted to constrain connectors onto the printed circuit board during a reflow assembly process. In addition, the slot is dimensioned to only house a printed circuit board having properly aligned connectors.
In another embodiment of the invention, an alignment fixture is constructed to include a slot, a claw and a first finger clamp. Connectors are inserted onto an edge of a printed circuit board. The circuit board is then transferred to the slot in the alignment fixture. The slot is dimensioned to fit only a circuit board having properly aligned connectors. The properly aligned circuit board is then fitted into the slot. The connectors are then constrained onto the circuit board with the claw. The claw is coupled to the alignment fixture via the first finger clamp. Using a reflow oven, the constrained connectors are then soldered onto the circuit board.
A more complete understanding of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the embodiment. Reference will be made to the appended sheets of drawings, which will first be described briefly.